Gravity-davit



Filed Oct. 17. 1951 INVENTOR. 41-12026! us J; Murzck United StatesPatent Oifice GRAVITY -DA;VIT

Arnoldus-de Munck, Utrecht, Netherlandgassignbr to Mij. tot Yrwerving enExplrvan: Davitoctrooien Davit- Company N V., Utrecht, Netherlands, acorporation of the Netherlands Application October 17, 1951, SerialNo;251,804

Claims priority, application Netherlands October 18, 1950 2 Claims. (Cll9- -38) The invention relates to a gravity-davit for a lifeboat, whichdavit is provided with at least one roller track and with an arm at thelower endof which there are provided rollers cooperating with the-rollertrack.

In the known devices the roller track practically consists of twoseparate guideways, the foremost rollers cooperating. with one of thesaid guideways and the back rollers with the other guideway. This.construction has the drawback that the davit armwhen. lowered, will notbe able to tilt to a suflicient degree, since the back rollers 'vvillabut against the bottom of the guideway for the foremost rollers, sothat in order to turn the lifeboat sufiiciently outboard the said armmust be made comin which the common centre of gravity of the said davitand the boat is not situated high above deck, since in that case theboat will be suspended low above deck.

The present invention has for its purpose to provide a davit of the typedescribed above, which davit will satisfy the said requirement.

For this purpose, according to the invention, the guide way for therollers is made of a single uninterrupted profile, so that when the armis moved outboard, the foremost and the back pairs of rollers will runin the same guideway, whereby when the swung-out position has beenattained, the back pair of rollers will not abut against the guideway ofthe foremost pair of rollers.

It is also possible, according to the invention, for the back pair ofthe rollers to take, in the extreme swuug-out position, the place thatis taken by the foremost pair of rollers when in the inboard position.abutting of the back roller or the back pair of rollers against theguideway of the foremost roller or the foremost pair of rollers willbecome absolutely impossible so that the swinging arm will now be ableto swing much farther outboard, which in itself will result in the factthat the said arm may be much shorter and that in the inboard positionthe lifeboat can be positioned close above deck.

In order to prevent these drawbacks the guide-way consists of a straightpart and a curved part, or in case an angle is provided in the saidguide-way in which the foremost supporting rollers will partly turn overthe said angle, which would prevent the outboard movement, the saidforemost supporting rollers, according to the invention, may in theinboard position, be supported by a projecting lug or lid which issituated in alignment with one of the parts of the guide-way. The saidlug or lid is adapted to be tilted by the back pair of rollers when thearm is moved outboard. It is even possible to construct the said lug orlid in such a way that it may be completely tilted back by the backrollers.

In that case the Patented Apr. 24, 1956 t a In order to reduce as muchaspossible the forces required for moving the lifeboat outboard, it ispossible,

according to the invention, to shape the arm and the guideway in such amanner that the common centre of gravity of the boat. and the davit armwill, in theinboard position, be situated above the foremost pair ofrollers.

In order to explain the invention still more clearly,

an embodimentthereof will now be explained, by way of example, with theaidof the accompanying drawing, Fig.1. of which is aside view in whichthe davit has been drawn in the two extreme positions.

Fig. 2 is aside view of the guideway only.

In the said drawing the reference numeral 1 represents a life boatsuspended by means of pulleys and blocks in the present case from twodavit arms 2.

Eachof the said arms 2 is provided at its lower end with pairsof rollers3 and' 4. The said pairs of rollers move in. a guide way 5, whichguideway consists of a straight part 6 and a curved part 7. In Fig. 1the device is represented in the two extreme positions; In the inboardposition the pair of rollers 4 is situated in. the extreine leftportion. of the curved part 7 of the guide Way while the pair of frontrollers 3 are in cont-act with the straightpart 6 of the guide way. Whenthe boat is to be launched, the rollers will move through theirrespective parts of the guide way, whereby the davit arm 2 is dis placedin the outboard direction, while performing a tilting motion. The guideway is stationary and the construction of the arm 2 is so designed thatthe boat adjacent the davit arms has its keel as low as possible, thatis, slightly above the guide way 5.

Owing to the fact that the guide way 5 is built in a single piece, whichmakes it possible for the rear pair of rollers 4 to approach, to takethe place of or even to pass by the place occupied by the pair ofrollers 3, the

arm 2, when being moved into the outboard position, will be able to tiltfurther outboard than is possible with the known constructions. In viewthereof it is possible that the keel of the boat may be positioned verylow relative to the deck. Also the davit arm extends quite a distance sothat the possibility is present of using a shorter davit arm, if it isdesired that the davit arm shall have a shorter reach.

On account of the above mentioned features the com mon centre of gravityof the boat and the davit arm will be located lower than with the knownconstructions.

Fig. 2 only represents the guide-way 5. 1n the said guide-way thestraight part and the curved part gradually merge into each otherwithout any interruption, the construction being such that in theoutboard position of the davit-arm the pair of rollers 4 will contactwith the curved part 8, while the pair of rollers3 will rest in the part9.

The construction may also be such that the pair of rollers 3 will travelalong a portion of the straight part 6 of the guide-way 5. This involvesmerely a modification in which the part 6 is a little longer than asshown in Figure 1 or the ends 8 and 9 are at a slightly further distancefrom one another. In this way, when the roller 3 is in the end at 9, theroller 4 will be slightly beyond the point 8 to the right. Thus, toachieve this possibility, it is only necessary that said portions 6 ofthe guideways must be made longer than in the embodiment shown in thedrawing. In other words, the length of the portions 8 to 9 of theguideways must then be greater than the distance between the rollers 3and 4 of the davit.

With the construction as shown use is made of a lug or fiap 10 the topsurface of which during the inboard position of the davit arm, issupported against the lower edge of the part 6 of the guideway.

In this position the pair of rollers 3 will be supported by the flap.The flap 10 is provided with a pivot 11 3 and with a projecting part 12extending into the guideway. When the arm 2 is moved outboard, the pairof rollers 4 will turn the said flap. The pivot 11 of the flap 10, 12 ismounted on the part 6 of the guideway. Part 12 of the flap reachesthrough an opening in the lower side of part 7 of the guideway into saidpart 7 in such a manner that in the position according to Figure 1, part12 of the flap forms an extension of part 6 of the guideway whichextension is located adjacent the sharp bend 8 and on which extensionthe roller 3 rests. Part 10 of the flap then bears against the lowerside of part 6 of the guideway, so that the flap cannot tilt backwardsunder the pressure of the roller 3. If now the davit is moved into theoutboard position, the roller 4 will run against the rear of part 12 ofthe flap just before said movement comes to an end, and said roller willforce part 12 to the right (as seen looking in the direction of movementof the davit arm) until roller 4 has reached the bend. When the davit isreturned to the inboard position, the flap is returned to its originalposition by roller 3.

When the davit arm is moved back, the pair of rollers 3 will cause theflap to move into its initial position.

I claim:

1. A gravity davit for a boat comprising a davit arm from one end ofwhich the boat is to be suspended and having a pair of spaced front andrear rollers at the other end, and a stationary base member for thedavit arm having a continuous guideway for the rollers with closed endsone for the inboard position of the davit arm and boat and the other forthe outboard position of the davit arm and boat, said guideway having aslightly curved bottom section and an upwardly-directed straight sectionfor the inboard position of the arm and a straight downwardly-directedportion for the outboard position of the arm with a sharp bend at thejunction of both straight section approximately at the mid-point of theguideway, the rear roller being at the closed end of the inboard part ofthe guide-way and the front roller at the sharp bend junction when thedavit arm is in the inboard position, and the rear roller being in thesharp bend junction of the guideway with the front roller at the otherclosed end when the davit is in the outboard position, and the guidewaybeing V-shaped in an inverted position, the apex of which V-shapedguideway constituting the sharp bend junction of both straight sections.

2. A gravity davit according to claim 1, in which a flap member isprovided pivotally mounted on the guideway at the sharp bend junction toproject into the path of the inboard section of the guideway to act as asupport for the front roller in the inboard position of the davit.

References Cited in the file of this patent UNITED STATES PATENTS581,925 Storm May 4, 1897 2,527,060 Dohn Oct. 24, 1950 FOREIGN PATENTS885,897 France June 15, 1943

